Dual Food Box Optional - 100/210ml: The 210ml large capacity food box can hold 100g fish food while the 100ml small one can hold 50g fish food. Choose one according to your going out time, keep enough food to feed your fish when you go out. Manual or Automatic Feeding: The automatic mode can set the time reasonably, feeding every 12 hours or every 24 hours, helping you to feed automatically when you are on vacation or business trip. Meanwhile, one-click manual feeding will not affect the preset times.(The product does not include battery) Two Installation Methods: For open aquarium, fix the feeder with the clamp, install it on the glass wall of the aquarium; for closed aquariums, attach one side to the aquarium lid, the other side to the feeder base, and glue the two sides together. Food Type Selection: This timer feeder can only be used for dry food. Ideal for pellet, strip, and flake fish food. Please place it above the upper tank to protect the food from moisture. Then fix the tank